Because of its ready availability and because of its relatively low cost and potential for reducing particulate emissions, compressed natural gas is a promising candidate for fueling diesel engines. Conventional me&:hods of fueling diesel engines by premixing air and natural gas appear to be inherently unsuitable for part load operation, at which the fuel-air mixture flammability suffers, efficiency drops substantially and emissions become excessive. In addition there is the problem of detonation under certain load conditions. These factors generally impose a limit on the feasible substitution of diesel fuel by natural gas in transport engines operating over a wide range of load and speed.